Method and apparatus for bringing laser chips to a measurement position

ABSTRACT

An apparatus for measuring output light intensity from laser chips mounted on respective carriers on a fixture, comprises a control unit for moving the fixture to in turn bring the chips to a measurement station, and a TV camera and a NIR camera both connected to a vision system for determining x and y coordinates of objects viewed by the TV camera and the NIR camera, respectively. The control unit is adapted to move the fixture to bring the respective chip in front of the TV camera to determine the coordinates of the chip on the fixture, move the fixture in response to the coordinates of the chip on the fixture to bring the chip in front of the NIR camera to determine the coordinates of a point of maximum light intensity from the ignited chip, and move the fixture in response to the coordinates of the point of maximum light intensity to bring the chip to the measurement station.

TECHNICAL FIELD

[0001] The invention relates generally to laser chips and morespecifically to a method and an apparatus for bringing a population ofmanufactured laser chips to a measurement position to select good laserchips, i.e. laser chips that fulfil an output light intensityrequirement.

BACKGROUND OF THE INVENTION

[0002] Manufactured laser chips are mounted on carriers. To test whetheror not the laser chips fulfil the requirement on output light intensity,the carriers with the chips are placed on a fixture that is moved to inturn bring the chips to a measurement station. This is a time consumingprocess in that the location of the point of maximum output lightintensity of a laser chip on a carrier is unknown. Therefore, at themeasurement station, each chip has to be scanned in order to locate thepoint of maximum output light intensity before the light intensity canbe measured. If for some reason a chip is missing in its expectedposition on the fixture, the scanning for the point of maximum outputlight intensity for that chip can continue until an operator notices thesituation.

SUMMARY OF THE INVENTION

[0003] The object of the invention is to more quickly locate the pointof maximum output light intensity of laser chips on carriers on afixture.

[0004] This is attained by the method according to the invention ofmeasuring output light intensity from laser chips mounted on respectivecarriers on a fixture, comprising moving the fixture to in turn bringthe chips to a measurement station in that, for each chip, the fixtureis first moved to bring the chip in front of a TV camera connected to avision system that is adapted to determine x and y coordinates ofobjects viewed by the TV camera, the coordinates of the chip on thefixture are determined by means of the vision system, the fixture isthen moved in response to the coordinates determined by the visionsystem to bring the chip in front of a NIR camera connected to thevision system that is adapted to determine also x and y coordinates ofobjects viewed by the NIR camera, the laser chip is ignited, and the xand y coordinates of the point of maximum light intensity from the chipare determined by means of the vision system, whereupon the fixture ismoved in response to the determined coordinates of the point of maximumlight intensity to bring the chip to the measurement station to measurethe light intensity.

[0005] This is also attained by the apparatus according to the inventionfor measuring output light intensity from laser chips mounted onrespective carriers on a fixture, comprising a control unit for movingthe fixture to in turn bring the chips to a measurement station (3), aTV camera and a NIR camera both connected to a vision system fordetermining x and y coordinates of objects viewed by the TV camera andthe NIR camera, respectively. The control unit is adapted to move thefixture to bring the respective chip in front of the TV camera todetermine the coordinates of the chip on the fixture, move the fixturein response to the coordinates of the chip on the fixture to bring thechip in front of the NIR camera to determine the coordinates of a pointof maximum light intensity from the ignited chip, and move the fixturein response to the coordinates of the point of maximum light intensityto bring the chip to the measurement station.

[0006] By the method and the apparatus according to the invention, theprocess of locating the point of maximum output light intensity of laserchips on carriers on a fixture will be much quicker than the processesused today.

BRIEF DESCRIPTION OF THE DRAWING

[0007] The invention will be described more in detail below withreference to the appended drawing on which the single FIGURE is aschematic illustration of an embodiment of an apparatus according to theinvention.

DESCRIPTION OF THE INVENTION

[0008] The FIGURE is a schematic illustration of an embodiment of anapparatus for bringing laser chips 1 mounted on respective carriers 2 toa measurement station 3 to measure output light intensity of the chips1.

[0009] In a manner known per se, the carriers 2 with the chips 1 aremounted on a fixture 4, and the fixture 4 is moved to in turn bring thechips 1 to the measurement station 3.

[0010] In the embodiment shown, the fixture 4 is driven by means of amotor (not shown), e.g. a linear motor, along a rod 5 under control of acentral control and signal processing unit 6.

[0011] In accordance with the invention, the fixture 4 is first movedalong the rod 5 to bring the first chip 1 in front of a TV camera 7. TheTV camera 7 is connected to a vision system 8 that is adapted todetermine x and y coordinates of objects viewed by the TV camera 7, andthat is connected to the central control and signal processing unit 6.

[0012] By means of the vision system 8, the coordinates of the chip 1 onthe fixture 4 is determined and transferred to the central control andsignal processing unit 6.

[0013] If a chip is missing on the fixture, this is detected by thevision system and the fixture is moved to bring the next chip in frontof the TV camera.

[0014] In response to the coordinates determined by the vision system 8,the central control and signal processing unit 6 controls the motor (notshown) to move the fixture 4 such that the chip 1 is brought in front ofa near infra-red (NIR) camera 9. The NIR camera 9 is also connected tothe vision system 8 that is adapted to determine x and y coordinates ofobjects viewed by the NIR camera 9.

[0015] In accordance with the invention, the laser chip 1 is nowignited, and the x and y coordinates of the point of maximum lightintensity from the chip 1 as viewed by the NIR camera 9 is nowdetermined by means of the vision system 8.

[0016] In response to the determined coordinates of the point of maximumlight intensity, the fixture 4 is moved such that the chip 1 is broughtto the measurement station 3 to measure the light intensity.

[0017] The measurement station 3 can be e.g. an optical fibre connectedto an input terminal of the central control and signal processing unit6.

[0018] Depending on whether the maximum light intensity of the chip 1 isabove or below a predetermined threshold, the chip 1 is accepted ordiscarded.

[0019] As should be apparent from the above, it is not necessary to scana “window” in order to locate the point of maximum light intensity of achip and, consequently, the apparatus according to the invention isquicker than the apparatuses known so far.

1. A method of measuring output light intensity from laser chips mountedon respective carriers on a fixture, comprising the steps of: moving thefixture to in turn bring the chips to a measurement station; wherein,for each chip, moving the fixture to bring the chip in front of a TVcamera connected to a vision system for determining x and y coordinatesof objects viewed by the TV camera; determining the coordinates of thechip on the fixture by means of the vision system; moving the fixture inresponse to the coordinates of the chip on the fixture to bring the chipin front of a NIR camera connected to the vision system for determiningx and y coordinates of objects viewed by the NIR camera; igniting thelaser chip; determining the coordinates of a point of maximum lightintensity from the chip by means of the vision system; and moving thefixture in response to the coordinates of the point of maximum lightintensity to bring the chip to the measurement station to measure thelight intensity.
 2. An apparatus for measuring output light intensityfrom laser chips mounted on respective carriers on a fixture,comprising: a control unit for moving the fixture to in turn bring thechips to a measurement station; a TV camera; a NIR camera both connectedto a vision system for determining x and y coordinates of objects viewedby the TV camera and the NIR camera, and that the control unit isadapted to move the fixture to bring the respective chip in front of theTV camera to determine the coordinates of the chip on the fixture, movethe fixture in response to the coordinates of the chip on the fixture tobring the chip in front of the NIR camera to determine the coordinatesof a point of maximum light intensity from the ignited chip, and movethe fixture in response to the coordinates of the point of maximum lightintensity to bring the chip to the measurement station.
 3. The apparatusaccording to claim 2, wherein the measurement station, the TV camera andthe NIR camera are arranged along a rod on which the fixture is moved.4. The apparatus according to claim 3, further comprising a motor todrive the fixture along the rod.
 5. The apparatus according to claim 4,wherein the motor is a linear motor.